The present invention relates to apparatus for testing plain or filter cigarettes or analogous articles (including plain or filter cigarillos, cigars, filter rod sections in the form of hollow tubes or wrapped fillers of fibrous or other filter material for tobacco smoke) which consist of and have open-ended tubular wrappers. More particularly, the invention relates to apparatus for testing the condition of tubular wrappers which form part of cigarettes or the like for the presence of absence of leaks in the form of open seams, tears, holes and/or similar defects. Still more particularly, the invention relates to apparatus for testing cigarettes or the like wherein the articles to be tested travel sideways during transport past a testing station where the wrappers of the articles are tested by means of a fluid medium.
It is already known to test cigarettes or like rod-shaped articles in an apparatus wherein the articles to be tested are transported sideways by a drum or another suitable endless conveyor which is provided with means for sealing the interior of the wrapper from its exterior during travel past the testing station. As a rule, the conveyor is provided with openings which are connected to a suction generating device so that the wrappers of articles to be tested are attracted to the conveyor by suction. A testing fluid is introduced into one or both ends of a wrapper which moves past the testing station, and the pressure of testing fluid is monitored by a suitable transducer which furnishes signals to an ejector whenever the pressure of testing fluid deviates from a range of pressures which are indicative of satisfactory wrappers. Thus, if a wrapper exhibits an open seam or a hole, the testing fluid escapes into the atmosphere and the pressure in the wrapper is below the minimum pressure which is still indicative of satisfactory wrappers.
All recent types of cigarette making machines embody one or more testing apparatus which are designed to determine the defects of cigarettes and to initiate the segregation of defective cigarettes from satisfactory cigarettes. The defects may include the aforementioned leaks in the wrappers, the absence of a filter plug or wrapped tobacco rod section in a filter cigarette, excessively compacted or loose tobacco fillers, improperly convoluted uniting bands which serve to connect the filter plug to the tobacco rod section of a filter cigarette, or soft tobacco-containing cigarette ends. Leaks in the wrappers are particularly irritating to the smoker because the taste of smoke changes considerably if a leaky wrapper allows atmospheric air to mix with tobacco smoke during flow of smoke into the mouth.
U.S. Pat. Nos. 3,408,858 and 3,533,279 disclose testing apparatus wherein the articles to be tested are transported by rotary drums which carry flutes wherein the articles rest during travel past the testing station. Each flute normally consists of three or more aligned cradles each of which is in contact with a large portion of the respective wrapper whereby the wrapper portions which contact the cradles cannot be tested for the presence or absence of leaks because the cradles seal or substantially seal the leaks in the wrapper portions which are in contact therewith. The drum carries coupling elements which engage the ends of wrappers during testing so that the air surrounding the exterior of a wrapper travelling past the testing station cannot flow into the interior of such wrapper or vice versa. The coupling elements further serve to admit into the wrappers a testing fluid which escapes through the holes, open seams or other leaks of the wrappers so that the pressure of testing fluid in a defective wrapper is less than a predetermined minimum pressure which is still indicative of a satisfactory wrapper. The pressure of testing fluid is monitored by one or more transducers which cause one or more ejectors to segregate the cigarettes with defective wrappers from satisfactory cigarettes.
A drawback of the just described testing apparatus is that if a cradle overlaps a hole in the wrapper of a cigarette which travels past the testing station, the testing fluid cannot escape by way of such leak so that the leak remains undetected. As mentioned before, the cradles of the drum-shaped testing conveyor are provided with relatively large article-contacting surfaces so that the likelihood of sealing of a leak during testing is quite pronounced.
Another drawback of presently known testing apparatus is that their conveyors are unable to properly retain the articles in optimum positions for testing when the articles must be tested at a rate at which they are being made in a high-speed producer, such as a cigarette rod making machine or a filter cigarette making machine which turns out up to and in excess of 70 articles per second. As a rule, the cigarettes are held by suction; however, when the centrifugal force is very strong due to high rotational speed of the conveyor of the testing apparatus, the cigarettes must be held by additional means, such as by the coupling elements which admit to their wrappers a testing fluid, whereby the additional retaining means are likely to deform and/or otherwise deface or damage the wrappers. If the articles are held by suction alone, the suction must be increased to an extent which can be achieved only by resorting to bulky, complex, expensive and extremely noisy compressors, pumps, fans or other suction generating devices.